Process for preserving wood



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OF GEARLO'ITENIBUBG, GERMANY, ASSIGNOE TO GRUBENEOLZ l BQGNIEBUNG G. K. B. H 01 GHABLOTTENBUBG, GERMANY rnocnss roe. ransnnvme ween m mm Application fled June a7, 1929, Serial No. 374,296, and in Germany July 3, 192a.

m when the water is evaporated. bimnarly it has already been proposed to impregnate the wood successively with two solutions, which are intended to react in the wood to form-dint w cultly soluble protective substances. The

known proposals of this kind have not proved satisfactory in practice, The solutions used in the tirst method were as a rule too unstable and readily decomposedmore especially at an increased temperature. In the case of the successive impregnation with two solutions in the manner above described, there was the dificulty that the reaction of the substances contained in the solutions only took 25 place incompletely in the wood, so that the object aimed at could not be attained.

llt has been found that it is possible to reduce the capacity of the watersoluble protectives introduced into the wood, for being c leached out, it the wood is impregnated successively with two solutions, the constitutents of which do. not torm insoluble or dificulty soluble compounds, but one solution contains substances which reduce the solubilit in wai-' 1 teroi the substances contained in t e other solution. F or carrying out the invention for instance the wood is first ofall treated with an approximately 2.0% solution of sodium fluosilicate and subsequently impregnated to with a 4.0% solution of common salt. When the wood is dried, a mixture of sodium fluosilicate and common salt remains therein. H the wood now comes into contact with water,

the common salt which is readily soluble in a water, passes into solution and thus makes ditucultly soluble compounds are precipitated the the leaching out of the sodium fluosilicace .diflicult, as this salt is much more difficultly soluble in a solution of sodium chloride than in water alone. In a similar manner the wood can first of all be impregnated with an aqueous, solution of sodium fi-naphthalene sulphonate and then with a solution of common salt or for carrying out the double impregnation use may be made of any other solutions desired. The same must behave in the manner indicated above, viz the constituents contained in one solution reduce the solubility of the substances dissolved in the other solution, which are to be rendered diflicult to wash out.

As a rule it will be advisable first of all to introduce into the wood the substances which serve to protect the wood and which are to be rendered difiicult to leach out troduction of the other solution. solution is preferably introduced by an empty cell process, so that durin the first impregnation as far as possible on the cell walls of the wood are uniformly soa ed in all penetrable portions. This is then followed by the introduction of the second solution preferably by the full cell process. As empty cell recess use may be made for instance of Patent No. 138933, but any other empty cell process can also be used. The second solution instead oi being introduced into the wood by the full cell process can also be introduced by the immersion process (by steeping the by the inhis first I iiping process described in German wood in the liquor in open receptacles).

This method is particularly advisable when the constituents of the second solution attack 1ron.

The wood can also be treated in the reverse order, that is to say the solution which makes it dificult to leach outthe preservatives can be introduced into the wood first, and the latter impregnated subsequently with the solution or these protective substances. The proportions ofthc substances contained in the two solutions are chosen from case to case according to the properties of the substances used; for instance the substances concerned can be used in approximately equivalent pro- 2 make it difficult for the preservatives to be leached out, will be introduced into the wood.

' Example is first of all exposed to an air pressure of 7 wood, such as for instance ammonium salts,

use of the said substances the methods described. ,On the contrary it 3 atms. and then while maintaining this air pressure a 2% solution of sodium fluosilicate is forced at a temperature of C: under a liquid pressure of 8 atms. into the vat. This liquid pressure isxmaintained for an hour, then the liquid is drained 'ofl and'the vat'exhausted. The amount of liquor thus extracted from the wood is drained out of the vat. It is then exhausted again. After a quarter of an hoursivacuum of at least 60 cmsfa 4.0% solution of common salt is introduced 2 into the vat, and this solution is forced into .the vat. until the pressure reaches 8 atms.

This pressureeis maintained for 2 hours, whereupon the steeping of the tion of common salt is also preferably used in a hot state at a temperature of 70 C.

For the purpose of preventing leaching out, use may be made," as already mentioned, of anycompounds which are capable of reducing the solubility of the protective substances. Preferably however for this purpose use will be made of salts, which in themselves also have a protective action on wood, for instancezinc salts or substances having the property of reducing the inflammability of boron compounds etc. T My invention is not limited either to the or to the use of relates broadly to preventing or making diflicultthe leaching out of the preservatives introduced into the wood by successive impregnation with substances having the properties described above. By preservatives 1 mean in my application organic substances capable of protectin wood against the attack of destructive fungl or insects such as for instance termites or against catching fire easily.

What I claim is 1 1. Afprocess for making it difiicult; to wash out the water-soluble protective substances introduced into'wood, consisting in introducing a solution of protective substances into wood and also introducing a separate solution of substances which do not broadly all organic or in-*- mimae form difiicultly soluble compounds with the but reduce their soluprotective substances,

as set forth.

process for making it diflicult to wash water, an have a protective action against organisms and other destructive influences,

r V, such asfire, as set forth. The wood contained in an iron steeping vat 1 3. A; process as claimed in claim 2 and in which te first solution is introduced into the wood according to an empty cell process, as set forth.

' 4. A which wood the first solution is introduced into the according to an emntv-cell nr'nnes's and the second solution according to the full cell process, as set forth. 7

In testimony whereof I have signed my name to this specification. 1

T DESIDER'STEINHERZ.

liquor is drainedqoff and the Q .wood is finished. Thesoluprocess as claimed in claim 2 and in 

